Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$248.38	10.765%	$275.1181	$275.12	$275.10	$275.10
Purchase #2	$54.56	9.130%	$59.5413	$59.54	$59.55	$59.50
Purchase #3	$99.25	9.776%	$108.9527	$108.95	$108.95	$109.00
Purchase #4	$111.69	10.409%	$123.3158	$123.32	$123.30	$123.30
Purchase #5	$81.48	13.495%	$92.4757	$92.48	$92.50	$92.50
Purchase #6	$195.66	8.671%	$212.6257	$212.63	$212.65	$212.60
Purchase #7	$144.60	7.214%	$155.0314	$155.03	$155.05	$155.00
7 purchase totals =	$935.62		$1,027.0607	$1,027.07	$1,027.10	$1,027.00